High permeate flux of PVA/PSf thin film composite nanofiltration membrane with aluminosilicate single-walled nanotubes

A new type of thin film nanocomposite (TFN) membranes for nanofiltration was successfully prepared by incorporating aluminosilicate single-walled nanotubes (SWNTs) within the poly(vinyl alcohol) (PVA) matrix. The nanocomposite PVA film was composed of well dispersed synthesized aluminosilicate SWNT with up to 20% volume fraction cast on a polysulfone support. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) revealed that the TFN membranes have characteristic bands at 920–1010 cm−1 corresponding to SiOH and SiOAl stretching vibration of the aluminosilicate SWNT. This insinuated the successful incorporation of aluminosilicate SWNT into the polymer matrix, which was further confirmed and quantified by X-ray photoelectron spectroscopy (XPS). The PVA layers, in the range of 0.99–1.36 μm, are free from large defects or cracks as observed in the scanning electron microscopy (SEM) images. The membrane surface hydrophilicity increased as the membrane roughness decreased and as the contact angles decreased from 64.2° to 59.4–50.5°. The increase in water flux is due to the presence of hydrophilic nanotubes. With the incorporation of the aluminosilicate single-walled nanotubes, higher permeate water flux was achieved, while sustaining high rejection of divalent ions (97%) and monovalent ions (59%).

Figure optionsDownload high-quality image (151 K)Download as PowerPoint slideHighlights
► Thin film nanocomposite NF membrane with aluminosilicate SWNT is fabricated.
► Membrane hydrophilicity increased with additional OH groups from the nanotubes.
► SWNT incorporation in PVA increased the pure water permeance of the TFN membranes.
► High permeate flux is due to preferential water flow through hydrophilic nanotubes.
► SWNT inclusion enhanced rejection of SO42- ions and partial rejection of Cl− ions.